1. Field of the Invention
The invention relates to a current mirror circuit being provided with a current mirror, an input and an output of which are coupled to an input and an output, respectively, of the current mirror circuit, and a limiter circuit comprising a reference current source and a unilaterally conducting element which includes a transistor, an emitter or source electrode of which is coupled to the input of the current mirror circuit.
The invention also relates to a video output amplifier circuit provided with the current mirror circuit.
2. Description of the Related Art
A current mirror circuit and a video output amplifier circuit of the type described above are known from European Patent Application EP-A No. 0.196.694 (PHN 11.504). To limit the dissipation in this circuit, the output current of the current mirror circuit is limited by connecting its input to a negative feedback input of a differential amplifier, an output of which is connected to said negative feedback input via the unilaterally conducting element. The other input of the differential amplifier is connected to a reference voltage which is generated by passing a reference current supplied by the reference current source through an impedance which is similar to an input impedance of the current mirror. In the case of a too large current, the differential amplifier and the unilaterally conducting element, which may be both a diode and a base-emitter junction (or gate-source junction) of a transistor in the known circuit, then constitute a negative feedback signal path which maintains the output current constant at a maximum valve which is determined by the reference current.
Although the output current is limited at this maximum value, an unwanted power dissipation is still found to appear in the case of given signal waveforms.